It is an everyday occurrence.A woman in the midwestern United States sprays her rosebushes to kill aphids. Cotton farmers in California fight the insidious boll weevil. In Mozambique, children sleep under nets that have been treated to protect them against disease-carrying mosquitoes.

All are using pesticides, chemicals designed to kill destructive pests such as insects, weeds, and fungi.These chemicals have helped save crops all over the world from destruction, yet they may be harming the environment and endangering human health. As a result, some people wonder if these chemicals should be used on crops and in people's homes.

Pesticides Today

The term pesticide covers three major types of chemicals. Herbicides, which kill weeds, are the most widely used. Next come insecticides, which kill insects, and then fungicides, which kill molds that grow on fruits...